Flexible rod manufacturing apparatus and method for a spinal fixation and the flexible rod manufactured through the same

ABSTRACT

The present invention relates to a rod capable of securely connecting pedicle screws in a pedicle screw system for correcting a damaged or transformed spine and a method and an apparatus for fabricating the same and, more particularly, to a flexible pedicle rod with superelasticity in order to provide a flexibility to a fixation between spine segments and a method and an apparatus capable of fabrication the same in mass production. The apparatus according to the present invention comprises a body; an X- and Y-axis moving element mounted on a top surface of the body, the X- and Y-axis moving element simultaneously moving in X-axis and Y-axis directions to wind a material at an angle of 90 degrees; a magazine mounted on the X- and Y-axis moving element to load a material; a material withdrawing element for withdrawing materials one by one from the magazine; and a material molding element mounted on the X- and Y-axis moving element, the material molding element gripping both ends of the material withdrawn from the material withdrawing element and rotating to mold a portion of the material in a spring shape.

BACKGROUND OF THE INVENTION

The present invention relates to a rod capable of securely connectingpedicle screws in a pedicle screw system for correcting a damaged ortransformed spine and a method and an apparatus for fabricating the sameand, more particularly, to a flexible pedicle rod with superelasticityin order to provide flexibility to a fixation between spine segments anda method and an apparatus capable of fabricating the same in massproduction.

Generally, when the spine undergoes bad environments of artificialfactors and degenerative spine disease and is maintained in abnormalpostures for a long time, serious back pain is induced by the press ofthe nerve system passing through the spinal canal.

In general, in the case where the conservative treatment has an effecton the patients with degenerative spine disease, the patients need thesurgical treatment. Particularly, a spinal fusion treatment is carriedout in spinal stenosis, spondylolisdthesis and spondylolysisaccompanying instability between spinal segments. A conventionalsurgical treatment to use a rigid rod, which does not have mobility atall, gives rise to many side effects on the patients as time goes on.Therefore, a pedicle fixing apparatus is to be inserted into an injuredor wrenched site of the spine in order that the injured or wrenched siteis neither suppressed nor is ruined or the part thereof is not pressedor pushed down.

As shown in FIGS. 1 and 2, a conventional pedicle fixing apparatusincludes a plurality of pedicle screws 200 which are respectivelyinserted, as a supporting member, through the pedicle into injured ordeformed vertebra, wherein each of the pedicle screws 200 has a head 201with a U-shaped rod passage 201 a; rods 250 for making a correction ofthe pedicle through an interconnection between the pedicle screws 200;set screws 300 to be inserted into the rod passage 201 a for fixing therods 250; and a transverse link 400 for holding a pair of the rods 250.

In the pedicle fixing apparatus of FIG. 1, the rod plays an importantrole in the fixation of the deformed vertebra. Therefore, the quality ofthe material, elasticity, and so on, of the rod has a significantinfluence on the human body.

Since most conventional rods are formed out of a titanium material for amedical treatment, the rods themselves do not have elasticity. There isa problem in that it is difficult to maintain a normal waist curvebecause the fusion of the spine segments is conducted according to theshape of the rod after the surgical spine correction. Moreover, afterthe spine completely fuses to the arrangement form of the rod, since aload is concentrated on the upper segment or the lower segment of thespine into which the pedicle screws are inserted, instability andanother stenosis can be caused after several years.

To solve the demerit of the rigid rod, various methods to partiallyprovide elasticity to a part of the rod have been introduced.Particularly, in order to solve the demerit of the conventional rodseffectively and to make the surgical correction of spinal deformityeasy, the applicant of the present invention introduced a rod for thepedicle fixation using a shape memory alloy such as a Ni—Ti alloy(Nitinol) which is harmless in the human body with high congeniality andhas the property similar to the human tissue in superelasticity andabsorption nature. For example, the various rods have been introduced inKorean patent application Nos. 2004-76105, 2004-76106, 2004-97833 and2004-97834.

As shown in FIGS. 3 a and 3 b, a rod (600) described in the citedreferences has a body 602 and an elastic member 604, which has a coiltype formed in the middle of the body 602, to provide the flexibility tothe rod 600. This flexible rod has a length of approximately 80 to 100mm (typically, 82 mm) and a small standard diameter of approximately 3to 6 mm. Since the material of the rod itself is to have the hard metalorganization and the rod is to be manufactured in a coil type with theshape memory through a heating process, it is very difficult to form theelastic member of the coil type in the middle of the rod. The rod havingthe coil section is manually made due to the drawback to the manufactureof the rod; however, it is very difficult to make the rod uniform and itis impossible to realize the mass production and commercialization.

On the other hand, when the surgical correction of spinal deformity, inwhich two parts of the rod body are different from each other in height,is performed, the elastic member having a large volume causes a surgicalinconvenience in the procedure of securing the rod within the pediclescrew because the body described in the cited references is positionedat the central axis of the elastic member and then the pedicle can be incontact with the elastic member. In this case, there is a problem inthat an inevitable operation procedure which has to dig a space out ofthe spine is required.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to providing anapparatus for fabricating a flexible rod of a pedicle screw system inmass production, wherein the fixation between spinal segments isimproved after the surgical correction of spinal deformity andsuperelasticity is provided for a part of the flexible rod in order thatan elastic power is induced when an external force is applied to thespine.

Also, embodiments of the present invention are directed to providing arod of a pedicle screw system, which has no interference from a elasticsection of the rod in the surgical correction of spinal deformity, byproviding eccentricity between a rod body and the elastic section.

According to an aspect to the present invention, there is provided anapparatus for fabricating a flexible pedicle rod for pedicle fixation,the apparatus comprising a body; an X- and Y-axis moving element mountedon a top surface of the body, the X- and Y-axis moving elementsimultaneously moving in X-axis and Y-axis directions to wind a materialat an angle of 90 degrees; a magazine mounted on the X- and Y-axismoving element to load a material; a material withdrawing element forwithdrawing materials one by one from the magazine; and a materialmolding element mounted on the X- and Y-axis moving element, thematerial molding element gripping both ends of the material withdrawnfrom the material withdrawing element and rotating to mold a portion ofthe material in a spring shape.

According to another aspect to the present invention, there is provideda method for fabricating a flexible pedicle rod for pedicle fixation,the method comprising a first step of initializing; a second step ofdriving a feeder driving motor to move a feeder straight in theinitialization state, thereby withdrawing a material from a magazine; athird step of gripping one end of the material moving straight by thefeeder at the die; a fourth step of driving an Y-axis servo motor builtin a body to move an Y-axis stage straight, thereby fixing the other endof the material to a groove shaft of a fixing base; a fifth step ofdriving a high-frequency heater to heat the material at a predeterminedtemperature; a sixth step of respectively driving Y-axis and X-axisservo motors in Y-axis and X-axis directions to wind the material fixedto the die and the groove shaft at 90 degrees; a seventh step of drivingthe X-axis servomotor to move an X-axis stage in the X-axis direction,and driving a rotating motor mounted on the X-axis stage to wind thematerial fixed to the fixing base on a spiral line and wind the materialin a coil shape; and an eighth step of discharging the material.

According to still another aspect to the present invention, there isprovided a flexible pedicle rod prepared by a process comprising a firststep of initializing; a second step of driving a feeder driving motor tomove a feeder straight in the initialization state, thereby withdrawinga material from a magazine; a third step of gripping one end of thematerial moving straight by the feeder at the die; a fourth step ofdriving an Y-axis servo motor built in a body to move an Y-axis stagestraight, thereby fixing the other end of the material to a groove shaftof a fixing base; a fifth step of driving a high-frequency heater toheat the material at a predetermined temperature; a sixth step ofrespectively driving Y-axis and X-axis servo motors in Y-axis and X-axisdirections to wind the material fixed to the die and the groove shaft at90 degrees; a seventh step of driving the X-axis servo motor to move anX-axis stage in the X-axis direction, and driving a rotating motormounted on the X-axis stage to wind the material fixed to the fixingbase on a spiral line and wind the material in a coil shape; and aneighth step of discharging the material.

According to still another aspect to the present invention, there isprovided a flexible pedicle rod comprising a straight-line portion,wherein one end of the straight-line portion is formed on a straightline and the other end of the straight-line portion is formed on thesame straight line; and a spring-shaped elastic portion wound in aspiral shape at a predetermined portion between the straight-lineportions, wherein the elastic portion and the rod body are formed to beeccentric by a predetermined interval.

As described in one embodiment of the present invention, a major featureof the present invention is to produce in large quantities of pediclerods each having a coil-shaped elastic portion from the conventionalrigid rod with no elasticity.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thesubject matter of the present disclosure will be more clearly understoodfrom the following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of a conventional pedicle fixing apparatushaving a pedicle screw system for a surgical correction of spinaldeformity;

FIG. 2 is a perspective view of a conventional pedicle fixing apparatusinstalled in vertebrae lumbales;

FIGS. 3 a and 3 b are views illustrating flexible pedicle rods used inthe conventional pedicle fixing apparatus;

FIGS. 4 to 6 are front, right lateral and left lateral views of anapparatus for fabricating a flexible pedicle rod according to thepresent invention;

FIG. 7 is a flow chart illustrating a method for fabricating theflexible pedicle rod according to the present invention;

FIG. 8 is a schematic view illustrating a fabricating procedures of theflexible pedicle rod according to the present invention; and

FIG. 9 is a perspective view of the flexible pedicle rod according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to accompanying drawings.

A apparatus and a method for fabricating a flexible pedicle rod forpedicle fixation according to one embodiment of the present inventionare implemented to produce in large quantities of pedicle rods in thestate that a superelastic force is applied to a portion of each of thepedicle rods.

A material for a pedicle rod used for the apparatus according to the oneembodiment of the present invention is fabricated using a shape-memoryalloy that does not harm human beings in various types of shape-memoryalloys, particularly Nitinol (i.e., Ni—Ti alloy). The present inventionis not limited to a pedicle rod using Nitinol. That is, a metal thatdoes not harm human beings, e.g., a titanium-based metal (including analloy), a stainless 316 (SUS 316) metal or the like may also be used tofabricate a pedicle rod according to one embodiment of the presentinvention.

As illustrated in FIGS. 4 to 6, an apparatus for fabricating a flexiblepedicle rod includes a body 2 having a Y-axis servo motor (not shown)built therein; a Y-axis stage 4 mounted on a top surface of the body 2to move in a Y-axis direction by means of a driving force of the Y-axisservo motor; an X-axis servo motor 6 mounted on one side of the body 2;an X-axis stage 8 mounted on the Y-axis stage 4 to move in an X-axisdirection by means of a driving force of the X-axis servo motor; amagazine 10 mounted on the Y-axis stage 4 at a predetermined inclinationangle to load a material; a feeder 12 mounted at a rear end of themagazine 10 to withdraw materials loaded to the magazine 10 by movingthem forward one by one; a feeder driving motor 14 for providingrotation power to the feeder 12 such that the feeder 12 can moveforward; a first timing belt 15 for connecting between the feeder 12 andthe feeder driving motor 14 to deliver power; a die 16 mounted in frontof the feeder 12 to grip a rear end of a material supplied by means ofthe operation of the feeder 12; a high-frequency heater 18 mounted atone side of the feeder 12 to provide a predetermined heat source to amaterial through a coil 18 a wound on an outer circumferential surfaceof the die 16 and then moving to a heating position of the material bymeans of a driving force of the Y-axis servo motor 6; a fixing base 20mounted on the Y-axis stage 4 and having a groove shaft 20 a mounted ata front side of the fixing base 20, the groove shaft supporting amaterial by fixing the other end of the material thereto; a C-axis motor22 for providing a rotation force to the fixing base 20 to wind amaterial in a spiral shape; a second timing belt 23 for connectingbetween the groove shaft 20 a of the fixing base 20 and the C-axis motor22 to deliver power; and a cylinder 24 mounted at a rear of the fixingbase 20 to discharge a molded material from the groove shaft 20 a bymoving straight toward the groove shaft 20 a. Reference numeral 26denotes a controller panel.

In the aforementioned configuration, since the C-axis motor 22 ispositively and reversely rotatable, an elastic portion formed in thematerial can be molded in the shape of a string wound in a left or rightdirection.

Hereinafter, fabricating processes using the apparatus for fabricating aflexible pedicle rod according to the one embodiment of the presentinvention will be described in detail with respect to FIGS. 7 and 8.

First, a power source switch (not shown) mounted on the controller panel26 is turned on, thereby initializing the apparatus (S10). If the feederdriving motor 14 is operated after loading a material to the magazine 10in the initial state of the apparatus, the feeder 12 moves straight towithdraw the material toward the die 16 (S20). One end of the withdrawnmaterial is gripped by the die 16, and the other end of the withdrawnmaterial is fixed to the groove shaft 20 a of the fixing base 20opposite to the die 16 on an axis line, thereby completing the setup ofthe material (S30) ((a) to (d) of FIG. 8).

In the embodiment of the present invention, an interval at which bothends of the material are gripped is about 15 mm. After completing thestep S30, the high-frequency heater 18 and the coil 18 a of thehigh-frequency heater 18 heat the material withdrawn from the die 16while moving by means of the operation of the Y-axis servo motor (S40)((c) and (d) of FIG. 8). At this time. The temperature at which thematerial is heated by the high-frequency heater 18 is about 600 to 700°C. If the heating temperature of the material is 600° C. or less, it isdifficult to obtain a molded product having a desired shape. If theheating temperature of the material is 700° C. or more, a change inproperty of the material may be caused.

When the heating of the material is completed, the Y-axis and X-axisservo motors are simultaneously driven. Accordingly, the Y-axis andX-axis stages 4 and 8 move in the Y-axis and X-axis directions,respectively. Through the operations of the Y-axis and X-axis stages 4and 8, the X-axis stage 8 is rotated in a direction of 90° about the die16, and the material having both ends fixed to the die 16 and the grooveshaft 20 a of the fixing base 20 is primarily bent at an angle of 90°(S50) ((e), (f) and (g) of FIG. 8).

After completing the primary winding of the material, the C-axis motor22 is rotated and driven, and the X-axis stage 8 moves and rotates thematerial three times on a spiral line, thereby performing a secondarywinding (S60) ((h) and (i) of FIG. 8). Through the operation, thematerial forms an elastic portion in a spring shape through. At the stepS50, since the C-axis motor 22 is positively and reversely rotatable,the elastic portion forms a spring wound in a right screw direction in apositive rotating operation, and forms a spring wound in a left screwdirection in a reverse rotating operation.

After completing the spring molding of the material, a gripping force iseliminated from the die 16 ((j) of FIG. 8). The Y-axis stage 4 moves bydriving the Y-axis motor, thereby leaving the material from the die 16.If the cylinder 24 moves straight to pass through the groove shaft 20 aof the fixing base 20, the molded material fixed to the groove shaft 20a is discharged (S70) ((k) of FIG. 8).

After discharging the material as described above, compressed air isprovided to the die 16 from the outside, thereby cooling the die 16(S80).

As illustrated in FIG. 9, a flexible pedicle rod 30 fabricated throughthe aforementioned configuration and fabricating method includes a rigidrod body 31 having a straight line shape and a flexible elastic portion32 having a spring shape. At this time, the pedicle rod 30 is formedinto an eccentric structure in which the center of the rod body 31 has apredetermined deviation t with respect to the center of the elasticportion 32. Since the heights of screws implanted into a pedicle aredifferent from one another in a vertebral pedicle correcting operation,the pedicle rod 30 prevents the elastic portion 32 from being interferedby the pedicle when the pedicle rod 30 is seated on the pedicle. Thatis, when the pedicle rod 30 is fabricated in the state that the centerof the rod body 31 is positioned on the same line with respect to thecenter of the elastic portion 32, a circumferential surface of theelastic portion 32 contacts the pedicle in the process of seating thepedicle rod 30 into a receiving groove of each of the screws withdifferent heights. For this reason, it is difficult to seat the pediclerod 30, and a vertebral bone may be unavoidably cut down by an intervalat which the elastic portion 32 contacts the pedicle. However, since theelastic portion 32 can face upward in the pedicle rod 30 havingeccentricity as described in the one embodiment of the presentinvention, interference between the elastic portion 32 and the pedicledoes not occur.

In addition, since the flexible pedicle rod 30 is flexible only at theelastic portion 32 and the rod body 31 is a rigid part,three-dimensional flexibility can be provided even though an erroroccurs in the process of connecting the pedicle rod 30 after the implantof the pedicle screws.

As described above, according to one embodiment of the presentinvention, a pedicle rod having a relatively short length and a rigidproperty is provided with a flexible elastic portion, and it is possibleto produce in large quantities of pedicle rods with such a structure, sothat the pedicle rods can be remarkably commercialized in a pediclecorrecting operation.

The pedicle rod provided with an elastic portion fabricated according toone embodiment of the present invention is deformed at a predeterminedtemperature and formed of a memory-shape alloy (nitinol) withsuperelasticity so that flexibility and durability can be maximized, andan operation can be easily performed due to flexibility caused at adeformation temperature of 10° C. or less, possessed by the shape-memoryalloy. Further, the present invention provides a pedicle fixingapparatus using a pedicle rod provided with an elastic portion and anoble connection method for fixing the pedicle rod with segments, sothat instability between spinal segments are cured, and exercise betweenthe spinal segments can be maintained. In addition, a side effect of anoperation using the conventional rigid rod can be reduced, and anoperation can be easily performed.

Although preferred embodiments of the present invention have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1-6. (canceled)
 7. A method for fabricating a flexible pedicle rod forpedicle fixation, comprising: a first step of initializing; a secondstep of driving a feeder driving motor to move a feeder straight in theinitialization state, thereby withdrawing a material from a magazine; athird step of gripping one end of the material moving straight by thefeeder at the die; a fourth step of driving an Y-axis servo motor builtin a body to move an Y-axis stage straight, thereby fixing the other endof the material to a groove shaft of a fixing base; a fifth step ofdriving a high-frequency heater to heat the material at a predeterminedtemperature; a sixth step of respectively driving Y-axis and X-axisservo motors in Y-axis and X-axis directions to wind the material fixedto the die and the groove shaft at 90 degrees; a seventh step of drivingthe X-axis servo motor to move an X-axis stage in the X-axis direction,and driving a rotating motor mounted on the X-axis stage to wind thematerial fixed to the fixing base on a spiral line and wind the materialin a coil shape; and an eighth step of discharging the material.
 8. Themethod of claim 7, wherein the fourth step is carried out at a heatingtemperature of 600 to 700° C.
 9. The method of claim 7, wherein thematerial at the seventh step is wound three times in the coil shape. 10.The method of claim 7, further comprising a ninth step of providingcompressed air to the die to cool the die after performing the eighthstep. 11-12. (canceled)